Spark plug



4, 1931' G. H. E. BERTHOLD 1,817,505

S PARK PLUG Filed Fe b. 9. 192a INVENTOR BER r/yoz 0 ATTORNEXS,

Patented Aug. 4, 1931 ,UNITED STATES PATENT OFFICE GEORGE E. E. BEBTHOLD, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO THE RAJAH COMPAN Y, OF

BLOOMFIELD, NEW JERSEY, A CORPORATTON OF NEW JERSEY SPARK PLUG Application filed February 9, 1928. Serial No. 252,997. I

This invention relates to new and useful improvements in igniting devices, and it pertains more particularly to spark plugs such as employed for igniting the charge in the cylinder of an internal combustion motor. Spark plugs as generally constructed con- 'sist of a metallic shell and a porcelain core, and the core is secured in position in the shell by means of a clamping bushing or nut which has threaded engagement with the shell and contact with the porcelain core to force it against an annular shoulder internally of the shell, the core having a shoulder for engagement with a suitable packing carried by the annular shoulder .of the shell. I

If, in the ordinary construction of spark plugs, all parts are accurately formed, they 3 2o are not liable to become damaged either in the assembling thereof, or during use of the plug. Such accuracy,

ways possible of attainment, principally because of the methods employed in the manufacture of the several parts, and it often happens that one or another of the arts will have defects such, for example, as s ight projections on the shoulders, or slight eccentricity of one or more of the parts. These imperfections, even though so slight asto be imperceptible often subject the core "to strains and stresses which result in a cracking thereof whenv attempt is made to rigidly secure the core in position in the shell, thus rendering the plug useless. Even though the imperfections may be so slight that in assembling the plug no damage oc- I curs, yet in operation when the several parts expand under the high temperature to which they are subjected, resulting strains tend to crack the core, thus rendering the plug inoperative.

This invention has for one of its objects to provide a novel construction in, spark plugs whereby the core of the plug is permitted to adjust itself with relation to the shell without producing strains or stresses on the core, thus eliminating the possibility of cracking or rupture of the core.

however, is not al- It is a further object of the invention to construct the several parts in such a manner that the core may, if necessary, assume a position out of alinement with the axis of the shell, and be secured in such position without subjecting the core to damaging strains or stresses.

'With these and other objects in view, the invention comprises the novel and improved features, constructions and combinations of partshereinafter described and particularly pointed out in the claims, the advantages of which will be readily understood and appreciated by those skilled in the art. 1

The invention will be clearly understood from the accompanying drawings illustrating the invention in one of its preferred forms, and the following description of the constructions therein shown.

In the drawings- The figure is a view partly in section and partly in elevation showing a spark plug constructed in accordance with t e present invention.

In the accompanying drawing, the shell is designated by the reference numeral 10 and as is the usual practice, a shell electrode 12 is employed. The shell is externally threaded as at 14 to rovide for its securement in position. The shell is also formed with an internally threaded portion 16 and at a point intermediate of its ends, the shell 10 is formed with an annular shoulder 18.

The core of the spark plug is designated by the reference character 20, and as is the common practice, this core 20 carries the central or core electrode 22 in such a manner that it will occupy a position adjacent the shell electrode 12 with all the parts in their assembled position. x

The core 20 is formed with an enlarged portion 24, which construction provides two oppositely disposed annular shoulders 26 and 28.

It will be noted that the diameter of the core 20 is such that said core does not contact at any pointwith the shell, and that the diameter of the enlarged portion 24 of the core is of such a diameter that the annular shoulder 26 will overlie the shoulder 18 of the shell. Interposed between the shoulders 18 and 26 of the shell and core respective y, there is a compressible packing gasket 30 which serves to prevent leakage of gas around the core when the parts are assembled to form the plug.

Surrounding the core 20, and resting upon the shoulder 28 there is a compressible packing gasket 32, and embracing the core 20 and the compressible packing gas ch32 there is a gasket compressing ring 3%. This compressing ring 34 is preferably rightangular in cross-sectional form, thus providing a portion 36 adapted for engagement with the packing gasket 32, and a skirt portion 38 which surrounds the enlarged portion 9i of the core 20.

The diameter of the packing compressing ring 3% is such that the portion 36 thereof does not engage or have contact with the reduced portion of the core 20, and the skirt portion 38 thereof will not engage or have contact with the enlarged portion 24: of the core 20. By reason of this construction the packing compressing ring is free to move in a lateral direction or radially of the core 20, within certain limitations without contact with the core. Said ring 3a may therefore be employed to compress the packing 32 between itself and the shoulder 28 without any tendency on the part of the ring to rigidly engage or position the core 20 relative to the shell 10.

The core 20 is secured in operative position within the shell by a bushing 40 which has threaded engagement with the threaded portion 16 of the shell. This bushing 40 surrounds the core 20, and its internal diameter is such that the bushing 40 does not engage the core 20 at any point and therefore there is no tendency on the part of the bushing 40 to centralize the core 20 with respect to the shell 10.

In addition to securing the core 20 in position in the shell 10, the bushing 40 serves to operate the compressing ring to place the packing 32 under compression, the inner end face 42 of the bushing engaging the portion 36 of the compressing ring 3i when the bushing is moved inwardly of the shell 10. The compressing ring 34 is preferably formed from relatively hard metal so that the inner end face d2 of the bushing may move relative to the ring without causing movement of the ring around the core, and to further insure this action, the inner end face of the bushing it) has its transverse dimension reduced, preferably by beveling the side edges thereof as shown at a l.

From the foregoing description it will be apparent that the present invention provides a spark plug in which the core may be rigidly secured in position within the shell of the plug without subjecting the core to binding action or strain which might result in cracking or rupture thereof. This result is obtained mainly by reason of the fact that the core is free to move relative to the shell 10 and the bushing 40, since it is not engaged by either, nor is it engaged by the packing compressing ring. Such a construction allows sufficient movement of the core relative to the shell to permit the core to adapt itself to any inaccuracies in the construction of either and it has been found that in actual practice the core may be secured in the shell with its axis considerably out of alignment with the axis of the shell without undue strain upon the core, and at the same time maintaining gas-tight joints between the shell and the core.

It is to be understood that the invention is not limited to the particular construction and arrangement of parts of the illustrated embodiment of the invention, but that the invention may be embodied in other forms within the scope of the claims.

Having explained the nature and object of the invention and having specifically described a construction embodying the invention in its preferred form what is claimed is:

1. A spark plug comprising an insulating core formed with a central part of wider diameter adapted to be engaged in a shell, a shell having a complementary recess to receive said wider part and a narrower bore to receive one end of the core, the bore and the recess being respectively wider than the prescribed diameters of the end and central part of the core by an amount at least sufficient to provide unobstructed clearance for any commonly occurring irregularity in such cores, relatively soft packing rings above and below said central part of the core, a relatively hard and substantially rigid bearing ring having its upper surface in a plane substantially normal to the axis of the core and fitting over one of said gaskets, means associated with said ring to resist radial extrusion of said gasket, said ring having radial clearance from the part of the core over which it is positioned sufficient to accommodate any commonly occurring irregularity thereof, and means for holding said parts tightly pressed together said means bearing upon the plane surface of said ring so as to permit lateral adjustment therebetween.

2. A spark plug comprising an insulating core formed with a central part of wider diameter adapted to be engaged in a shell, a shell having a complementary recess to receive said wider part and a narrower bore to receive one end of the core, the bore and the recess being respectively wider than the prescribed diameters of the end and central part of the core by an amount at least sufficient to provide unobstructed clearance for any commonly occurring irregularity in such cores, relatively soft packing rings above and below said central part of the core, a relatively hard and substantially rigid L- shapedbearing ring having its upper surface in a plane substantially normal to the axis of the core and its side fitting closely over the edge of one of said gaskets so as to resist radial extrusion thereof under the sealing pressure, said ring having substantial radial clearance from the part of the core over which it is positioned sufiicient to accommodate any commonly occurring irregularity thereof, and means holding said parts axially pressed together in pressure tight relation, said means bearing upon the plane surface of said bearing ring so as to permit lateral adjustment therebetween.

Signed at New York, N. Y., this 2d day of February, 1928.

GEORGE H. E. BERTHOLD. 

